U.S. patent number 7,597,470 [Application Number 11/827,069] was granted by the patent office on 2009-10-06 for illuminating device, and display device and portable electronic device having the same.
This patent grant is currently assigned to Seiko Instruments Inc.. Invention is credited to Makoto Kurihara.
United States Patent |
7,597,470 |
Kurihara |
October 6, 2009 |
Illuminating device, and display device and portable electronic
device having the same
Abstract
A plurality of display portions are illuminated in different
colors using a light source of a single type and a single light
guide plate. A light source (220) has a light emitting element for
emitting blue light, and a red fluorescent substance which is
excited by blue light to generate red light, thereby emitting
violet light (L1) as a whole. The violet light (L1) enters a side
surface of a light guide plate (210) and is emitted from an upper
surface (211) and a lower surface (212) as violet light (L1-1) and
(L1-2), respectively. A green fluorescent substance is provided in
a fluorescent film (230). The light (L2) obtained after the violet
light (L1-1) passes through the fluorescent film (230), becomes
white light because green color component light generated from the
fluorescent substance is mixed with the violet light (L1-1). On the
other hand, on a lower surface side, the violet light L1-2 is used
as illuminating light.
Inventors: |
Kurihara; Makoto (Chiba,
JP) |
Assignee: |
Seiko Instruments Inc.
(JP)
|
Family
ID: |
39050562 |
Appl.
No.: |
11/827,069 |
Filed: |
July 10, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080037282 A1 |
Feb 14, 2008 |
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Foreign Application Priority Data
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|
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Aug 9, 2006 [JP] |
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2006-217124 |
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Current U.S.
Class: |
362/616; 362/607;
362/612 |
Current CPC
Class: |
G02F
1/133621 (20130101); G02F 1/133617 (20130101); G02B
6/0073 (20130101); G02F 1/133342 (20210101); F21V
2200/20 (20150115); F21Y 2105/00 (20130101); G02F
1/133615 (20130101); F21V 2200/30 (20150115) |
Current International
Class: |
F21V
7/04 (20060101) |
Field of
Search: |
;362/84,231,602,606,607,612,618,627,628,800 ;257/98,99,100
;349/61,65 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lee; Y My Quach
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. A display device, comprising: a first display portion that has a
color filter; a second display portion; a light source having a
light-emitting element that emits light including a wavelength
which excites a fluorescent substance, and a transparent resin
mixed with the fluorescent substance for emitting a first light
having a different wavelength component when excited by light
emitted by the light-emitting element; a light guide plate having
an incidence surface through which the first light from the light
source enters, a first light-emitting surface for illuminating the
first display portion, and a second light-emitting surface for
illuminating the second display portion; and light conversion means
provided between the first display portion and the first
light-emitting surface for converting the first light to a second
light that has a color component different from a color component
of the first light, wherein the first display portion is
illuminated by white light obtained by mixing the first light and
the second light to perform a color display and the second display
portion is illuminated by the first light to perform a
monochromatic color display.
2. A display device according to claim 1; further comprising one of
a filter having a layer in which one of a pigment and a fluorescent
substance is dispersed, and a particular color light cutting filter
for cutting a particular color component among color components of
the first light emitted from the light source, which is provided
between the second light-emitting surface and the second display
portion.
3. A display device according to claim 1; wherein the first and
second display portions comprise liquid crystal displays.
4. A display device according to claim 3; wherein the light
conversion means comprises a color fluorescent substance which is
excited by the first light from the light source to generate the
second light having a color component different from a color
component of light from the light source and which generates white
light by mixing the first light emitted from the light source with
the second light having the color component different from the
color component of the first light.
5. A display device according to claim 1; wherein the first display
portion and the second display portion are disposed so as to face
each other with the light guide plate disposed therebetween.
6. A display device comprising: a first display that, when
illuminated with white light, exhibits a color display; a second
display that, when illuminated with light, exhibits a monochromatic
color display; a light source that emits a first light having a
first color component; a light guide plate having an incidence
surface on which the first light is incident, a first surface from
which first light exits the light guide plate, and a second surface
from which first light exits the light guide plate and illuminates
the second display so that the second display exhibits a
monochromatic color display; a light conversion element disposed
between the first display and the first surface of the light guide
plate and that converts first light exiting from the first surface
to white light that illuminates the first display so that the first
display exhibits a color display; and a color filter disposed
between the second display and the second surface of the light
guide plate and that has a layer in which is dispersed a pigment or
a fluorescent substance, wherein the second display exhibits a
monochromatic color display in a color different from the first
color component of the first light.
7. A display device according to claim 6; further including a
transflective plate disposed between the second display and the
second surface of the light guide plate.
8. A display device according to claim 6; wherein the first and
second displays are disposed in opposed relationship on opposite
sides of the light guide plate.
9. A display device comprising: a first display that, when
illuminated with white light, exhibits a color display; a second
display that, when illuminated with light, exhibits a monochromatic
color display; a light source that emits a first light having a
first color component; a light guide plate having an incidence
surface on which the first light is incident, a first surface from
which first light exits the light guide plate, and a second surface
from which first light exits the light guide plate and illuminates
the second display so that the second display exhibits a
monochromatic color display; a light conversion element disposed
between the first display and the first surface of the light guide
plate and that converts first light exiting from the first surface
to white light that illuminates the first display so that the first
display exhibits a color display; and a light cutting filter
disposed between the second display and the second surface of the
light guide plate and that cuts a particular color component among
color components of first light exiting the second surface, wherein
the second display exhibits a monochromatic color display in a
color different from the first color component of the first
light.
10. A display device comprising: a first display that, when
illuminated with white light, exhibits a color display; a second
display that, when illuminated with light, exhibits a monochromatic
color display; a light source that emits a first light having a
first color component, the light source comprising a light-emitting
element that emits light, and a fluorescent substance that when
excited by the light emitted from the light-emitting element
generates the first light; a light guide plate having an incidence
surface on which the first light is incident, a first surface from
which first light exits the light guide plate, and a second surface
from which first light exits the light guide plate and illuminates
the second display so that the second display exhibits a
monochromatic color display; and a light conversion element
disposed between the first display and the first surface of the
light guide plate and that converts first light exiting from the
first surface to white light that illuminates the first display so
that the first display exhibits a color display, the light
conversion element comprising a color fluorescent substance that,
when excited by the first light, generates a second light having a
second color component different from the first color component and
that mixes the first light with the second light to generate white
light.
11. A display device according to claim 10; wherein the light
conversion element comprises a fluorescent film in which is
dispersed the color fluorescent substance.
12. A display device according to claim 10; further including a
transflective plate disposed between the second display and the
second surface of the light guide plate.
13. A display device according to claim 10; wherein the first and
second displays comprise liquid crystal displays.
14. A display device according to claim 10; wherein the first and
second displays are disposed in opposed relationship on opposite
sides of the light guide plate.
15. A display device according to claim 14; wherein the display
area of the first display is larger than the display area of the
second display.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device having a
plurality of display portions.
2. Description of the Related Art
A liquid crystal display device is widely used as a display device
for various kinds of electronic devices such as a cellular phone, a
computer, a personal digital assistant, and a video game. Liquid
crystal display devices include reflective ones, transmissive ones,
and transflective ones. As a display device for a portable
electronic device such as a cellular phone described in the above,
a transmissive liquid crystal display device and a transflective
liquid crystal display device are widely used. Because a liquid
crystal display panel is a non self light emitting type display
element, an illuminating device (backlight) is necessary for a
transmissive or transflective liquid crystal display device.
Cellular phones include so-called folder type (flip type) ones.
FIG. 5 schematically illustrates a folder type cellular phone. FIG.
5A illustrates the cellular phone in an opened state while FIG. 5B
illustrates the cellular phone in a folded state. As illustrated in
FIGS. 5A and 5B, in this type of a cellular phone, a main body
portion 01 having a plurality of buttons disposed thereon and a
display portion 02 are connected by a hinge 03 so that the display
portion 02 is opened and closed with respect to the main body
portion 01. The display portion 02 has a main liquid crystal
display panel 04 disposed on an inner side when folded and an
auxiliary liquid crystal display panel 05 disposed on an outer side
when folded. Specifically, in the display portion 02, the main
liquid crystal display panel 04 and the auxiliary liquid crystal
display panel 05 are disposed back to back. In order to illuminate
the main liquid crystal display panel 04 and the auxiliary liquid
crystal display panel 05 from respective sides of the back surfaces
thereof, a main illuminating device and an auxiliary illuminating
device are provided in some cases.
When the main and auxiliary liquid crystal display panels are thus
illuminated by separate illuminating devices, because two
illuminating devices are necessary, costs and the number of parts
are increased, which raises problems of increased weight and
increased size. Therefore, products in which the main and auxiliary
liquid crystal display panels are illuminated by one illuminating
device for reduction in thickness are widely provided. In such a
product, a light guide plate is disposed between the main liquid
crystal display panel and the auxiliary liquid crystal display
panel. A light emitting diode emits light to a side surface of the
light guide plate. The incident light is emitted from a light
emitting surface on an upper surface side of the light guide plate
(surface on the side of the main liquid crystal display panel) and
from a light emitting surface on a lower surface side of the light
guide plate (surface on the side of the auxiliary liquid crystal
display panel) to illuminate the main and auxiliary liquid crystal
display panels. In this case, in order to make larger an amount of
light illuminating the large main liquid crystal display panel than
an amount of light illuminating the small auxiliary liquid crystal
display panel, a transflective sheet which partly transmits light
and partly reflects light is disposed between the light guide plate
and the auxiliary liquid crystal display panel in some cases (see,
for example, JP 2004-87409 A).
In the structure in which the main and auxiliary liquid crystal
display panels are illuminated by using one illuminating device,
because light is emitted from both surfaces of one light guide
plate, the color of the backlight of the main liquid crystal
display panel and the color of the backlight of the auxiliary
liquid crystal display panel are the same. Normally, the color of
the backlight (that is, the color of light emitted from the
illuminating device) is white. This is because a color liquid
crystal display panel can perform optimum color display by being
illuminated by white backlight.
However, while a color liquid crystal display panel is used as the
main liquid crystal display panel, a monochrome liquid crystal
display panel is used as the auxiliary liquid crystal display panel
in some cases. In such a case, the auxiliary liquid crystal display
panel can naturally perform only monochrome display and can not
perform chromatic display. If, although various colors are applied
to the main body portion and a case of the display portion of a
cellular phone, the auxiliary liquid crystal display panel only
performs monochrome display and can not perform chromatic display,
such a cellular phone is less attractive as a product. In order to
enhance the appearance of the cellular phone as a product (from the
viewpoint of design), it is effective that the monochrome liquid
crystal display panel is chromatically colored even if only in one
color.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a
double-sided display device capable of chromatic display using a
monochrome liquid crystal display panel in an electronic device for
illuminating a main color liquid crystal display panel and an
auxiliary monochrome liquid crystal display panel by one
illuminating device.
In order to solve the above-mentioned problems, according to an
aspect of the present invention, there is provided an illuminating
device including: a light source for generating light including a
wavelength which excites a fluorescent substance; a light guide
plate having a first light emitting surface and a second light
emitting surface for emitting light when light generated from the
light source enters an incidence surface thereof; and a whitening
film disposed in a path of light emitted from the first light
emitting surface and including a fluorescent substance for emitting
light having a color component for generating white light by being
mixed with light generated from the light source.
According to another aspect of the present invention, an
illuminating device uses a light source formed by sealing within a
transparent sealing resin, an LED element for emitting light
including a wavelength which excites a fluorescent substance. The
illuminating device includes a light guide plate formed of a
transparent resin in the shape of a plate for emitting light from a
first light emitting surface which is an upper surface and from a
second light emitting surface which is a lower surface when light
emitted from the light source enters a side surface thereof, and a
whitening film disposed at a position where light emitted from the
first light emitting surface passes and including the fluorescent
substance for emitting light having a color component which makes
light passing therethrough into white light by being mixed with the
light emitted from a light emitting diode.
According to still another aspect of this invention, an
illuminating device includes: a light source formed by sealing
within a transparent sealing resin with a fluorescent substance
added thereto a light emitting element for emitting light including
a wavelength which can excite the fluorescent substance; a light
guide plate formed of a transparent resin in a shape of a plate for
emitting light from a first light emitting surface which is an
upper surface and from a second light emitting surface which is a
lower surface when light emitted from the light source enters a
side surface thereof; and a whitening film disposed at a position
where light emitted from the first light emitting surface passes
and including a fluorescent substance for emitting light having a
color component which makes light passing therethrough white light
by mixing the light with light emitted from a light emitting diode.
Further, the whitening film has a fluorescent substance dispersion
layer where the fluorescent substance and transparent beads are
dispersed and mixed. The illuminating device further includes at a
position where light emitted from the second light emitting surface
a filter having a layer in which a pigment or a fluorescent
substance is dispersed, or a specific color light cutting filter
for cutting a specific color component of light. Further, as the
light emitting element, an LED for emitting blue light having a
peak wavelength of 450 to 470 nm or an LED for emitting
near-ultraviolet light is used.
According to yet another aspect of the present invention, a display
device is structured such that the main color liquid crystal
display panel and the auxiliary monochrome liquid crystal display
panel are disposed back to back with a space therebetween, and a
double-sided illuminating device is disposed between the main
liquid crystal display panel and the auxiliary liquid crystal
display panel with the first light emitting surface facing a back
surface of the main liquid crystal display panel and the second
light emitting surface facing a back surface of the auxiliary
liquid crystal display panel. Such a double-sided display device
can be incorporated into a display portion of a folder type
portable electronic device.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a sectional view of a display portion of a cellular phone
according to the present invention;
FIG. 2 is a schematic sectional view illustrating a structure of a
light source using an LED element;
FIG. 3 is an enlarged sectional view illustrating a fluorescent
film (whitening film);
FIG. 4 is a table illustrating exemplary combinations of a light
emitting element (LED element) and a fluorescent substance added to
a sealing material;
FIGS. 5A and 5B are schematic views each illustrating a general
folder-type cellular phone;
FIG. 6 is a sectional view of another example of a display portion
of a cellular phone according to the present invention; and
FIG. 7 is a sectional view of a further example of a display
portion of a cellular phone according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An illuminating device according to the present invention includes:
a light source for generating light including a wavelength which
excites a fluorescent substance; a light guide plate having a first
light emitting surface and a second light emitting surface for
emitting light when light generated from the light source enters an
incidence surface; and a whitening film disposed in a path of light
emitted from the first light emitting surface and including a
fluorescent substance for generating light having a color component
which becomes white light by being mixed with light emitted from
the light source. The structure makes it possible to illuminate a
side of the first light emitting surface in white and to illuminate
a side of the second light emitting surface with another color by
using a light source of a single type and a single light guide
plate.
In this case, the light source includes a light emitting element
for emitting light including a wavelength which excites a
fluorescent substance, and a transparent resin added with the
fluorescent substance for emitting light including another
wavelength by being excited by the light emitted by the light
emitting element.
Further, the whitening film has a fluorescent substance dispersion
layer in which the fluorescent substance and transparent beads are
dispersed and mixed. Therefore, part of light from the light source
passes through the transparent beads without fail, and thus, the
ratio of light which passes through the whitening film without
changing the color of light from the light source becomes higher.
Therefore, the brightness is improved, and the color of light which
passes through the whitening film becomes white without fail.
A display device according to the present invention includes: a
first display portion; a second display portion; a light source;
and a light guide plate having an incidence surface that light from
the light source enters, a first light emitting surface for
emitting light for illuminating the first display portion, and a
second light emitting surface for emitting light for illuminating
the second display portion. Light conversion means which is excited
by a wavelength component of light from the light source to emit
light is provided between the first display portion and the first
light emitting surface. This makes it possible to illuminate the
first display portion and the second display portion in differently
colored light. Specifically, a plurality of display portions can be
illuminated in different colors using a light source of a single
type and a single light guide plate. In this case, the light source
includes a light emitting element for emitting light including a
wavelength which excites a fluorescent substance, and a transparent
resin added with the fluorescent substance for emitting light
including another wavelength by being excited by the light emitted
by the light emitting element.
In this case, employed is the structure in which the first display
portion is provided in a color liquid crystal display element
having a color filter, the second display portion is provided in a
liquid crystal display element for performing monochrome display,
and the light conversion means can illuminate the color liquid
crystal display element with white light generated by converting
light from the light source. As a result, it is possible to
illuminate the color liquid crystal display element for performing
display of high color reproducibility and to illuminate the liquid
crystal display panel for performing monochrome display in colored
light by using a light source of a single type and a single light
guide plate. In this case, the light conversion means includes a
color fluorescent substance for emitting light having a color
component different from that of light from the light source by
being excited by light from the light source, and white light is
generated by mixing light from the light source with light having a
color component different from that of light from the light
source.
Further, a filter having a layer in which a pigment or a
fluorescent substance is dispersed or a particular color light
cutting filter for cutting a particular color component among color
components of light emitted from the light source is provided
between the second light emitting surface and the second display
portion. The structure makes it possible to illuminate the second
display portion in an arbitrary color independently of the color of
light emitted from the light source. For example, in order to
obtain white light most suitable for a liquid crystal display
device using a color filter, there may be only limited combinations
of the light source and the light conversion means. Even in such a
case, by providing the above-mentioned filter between the second
light emitting surface and the second display portion, the second
display portion can be illuminated in a color different from that
of the light source.
According to the present invention, a plurality of colors of
illuminating light can be obtained using a light source of a single
type and a single light guide plate. Therefore, a plurality of
display portions can be illuminated in different colors using a
light source of a single type and a single light guide plate.
Embodiments of the present invention are now described in detail in
the following with reference to the attached drawings.
Embodiment 1
FIG. 1 is a sectional view schematically illustrating a
double-sided display device according to Embodiment 1. As
illustrated in FIG. 1, a main color liquid crystal display panel
110 is disposed on one side of a case 101 of a double-sided display
device 100 while an auxiliary monochrome liquid crystal display
panel 111 is disposed on the other side of the case 101.
Specifically, the main liquid crystal display panel 110 and the
auxiliary liquid crystal display panel 111 are disposed back to
back with a space therebetween. In this case, the auxiliary liquid
crystal display panel 111 has an area smaller than that of the main
liquid crystal display panel 110. A planar double-sided
illuminating device 200 is provided between the liquid crystal
display panels 110 and 111.
A light guide plate 210 of the double-sided illuminating device 200
is a rectangular plate-like member formed of a transparent resin
such as an acrylic resin or a polycarbonate. An upper surface
(first light emitting surface) 211 of the light guide plate 210
faces a back surface of the main liquid crystal display panel 110
while a lower surface (second light emitting surface) 212 of the
light guide plate 210 faces a back surface of the auxiliary liquid
crystal display panel 111. Further, the area of the upper surface
211 and the area of the lower surface 212 of the light guide plate
210 are substantially the same as that of a display surface of the
main liquid crystal display panel 110.
A light source 220 having an LED element packaged therein is used
in the double-sided illuminating device 200. The light source 220
is disposed so as to face a side surface of the light guide plate
210. FIG. 2 illustrates a detailed structure of the light source
220. As illustrated in FIG. 2, the light source 220 according to
this embodiment is formed by sealing an LED element 222 disposed in
a case 221 within a transparent sealing resin 224 such as a
silicone resin or an epoxy resin with a red fluorescent substance
223 added thereto. It should be noted that a conductor wire 225 is
provided for driving the LED element 222.
The LED element 222 is an InGaN-based or GaN-based light emitting
element and emits blue light (light having a peak wavelength of 450
to 470 nm). The red fluorescent substance 223 is a fluorescent
substance for emitting red light. Specifically, an europium-doped
sulfide such as CaS:Eu or SrS:Eu, a nitride based fluorescent
substance such as CaAlSiN.sub.3:Eu, or an organic colored resin
fine powder is adopted. The red fluorescent substance 223 using
such a material is, when blue light is emitted from the LED element
222, excited by the blue light, and emits red light (fluorescent
light). In this way, in the light source 220, the LED element 222
emits blue light and the red fluorescent substance 223 emits red
light, so the light source 220 as a whole emits violet light
L1.
With reference to FIG. 1 again, the violet light L1 emitted from
the light source 220 enters the side surface of the light guide
plate 210, passes through the light guide plate 210, and is emitted
or exits from the upper surface 211 and the lower surface 212 which
are light-emitting surfaces. A light conversion element in the form
of a fluorescent film (whitening film) 230 is disposed between the
upper surface 211 of the light guide plate 210 and the main liquid
crystal display panel 110. Further, two prism sheets 241 and 242
for improving the brightness are disposed between the fluorescent
film 230 and the main liquid crystal display panel 110.
The fluorescent film 230 is a whitening film (light wavelength
conversion film) which has the function of making the color of
light L2 which passes through and out of the film white by
transmitting the violet light L1-1 emitted from the upper surface
211 of the light guide plate 210. A specific example of the
fluorescent film (whitening film) 230 is illustrated in FIG. 3. As
illustrated in the figure, the fluorescent film 230 is formed by
printing a transparent resin (fluorescent substance dispersion
layer) 234 such as an acrylic resin on an upper surface of a PET
(polyethylene terephthalate) film 231, disposing a PET film 235 on
an upper surface of the transparent resin 234, and further,
printing a transparent resin 237 such as an acrylic resin in which
transparent beads 236 are dispersed and mixed on an upper surface
of the PET film 235.
In addition, a green fluorescent substance 232 and transparent
beads 233 are dispersed and mixed in the transparent resin
(fluorescent substance dispersion layer) 234. The green fluorescent
substance 232 is, for example, SrGa.sub.2S.sub.4:Eu,
CaSrGa.sub.2S.sub.4:Eu, or an organic colored resin fine powder,
and emits green light when blue color component light is
irradiated. The light L2 emitted from the fluorescent film 230 is
white light because it is mixed light of the violet light (light
formed of blue color component light and red color component light)
L1-1 and green color component light emitted from the green
fluorescent substance 232.
It should be noted that red color component light of the violet
light L1-1 is, when it enters the green fluorescent substance 232
in the transparent resin 234, absorbed in or reflected by the green
fluorescent substance 232. Therefore, if the transparent beads 233
are not dispersed and mixed in the transparent resin 234 and only
the green fluorescent substance 232 is dispersed and mixed therein,
the amount of red color component light which passes through the
transparent resin 234 is greatly decreased, and there may be cases
where light which passes through the fluorescent film 230 does not
become white light. On the other hand, according to this
embodiment, because the transparent beads 233 are also dispersed
and mixed in the transparent resin 234, part of red color component
light passes through the transparent beads 233, and thus,
transmittance of the red color component light is improved. In this
way, the ratio of red color component light to the whole light
which passes through the fluorescent film 230 can be prevented from
being lowered, and, light which passes through the fluorescent film
230 becomes white light and the brightness of the white light L2
becomes higher.
Further, because the transparent beads 236 are dispersed and mixed
in the transparent resin 237, the diffusion and dispersiblity of
the white light L2 can be improved to attain uniform
brightness.
It should be noted that the fluorescent film (whitening film) is
not limited to the one illustrated in FIG. 3. If the film has at
least a fluorescent substance dispersion layer in which a
fluorescent substance is dispersed, and a color component light
emitted from the fluorescent substance and color component light
which enters the fluorescent film are mixed such that light which
goes through and out of the fluorescent film becomes white light,
other elements may be omitted.
With reference to FIG. 1 again, the white light L2 which passes
through the fluorescent film (whitening film) 230 passes through
two prism sheets 241 and 242 to improve its brightness, and
illuminates the color liquid crystal display panel 110 from the
side of its back surface.
A transflective plate 250 is disposed between the lower surface 212
of the light guide plate 210 and the auxiliary liquid crystal
display panel 111. Further, two prism sheets 243 and 244 for
improving the brightness are disposed between the liquid crystal
display panel 111 and the transflective plate 250.
The transflective plate 250 has the function of reflecting part of
the violet light L1-2 which enters the transflective plate 250 from
the lower surface 212 of the light guide plate 210 and transmitting
part of the rest of the light. Light reflected by the transflective
plate 250 again enters the light guide plate 210, and after that,
is emitted again from the upper surface 211 and the lower surface
212 of the light guide plate 210 as the light L1-1 and the light
L1-2, respectively. Therefore, the transflective plate 250
contributes to improvement in the brightness of the main liquid
crystal display panel 110 having a larger surface area. On the
other hand, the violet light L1-2 which passes through the
transflective plate 250 passes through the two prism sheets 243 and
244 to improve its brightness, and illuminates the monochrome
liquid crystal display panel 111 from the side of its back
surface.
As described in the above, according to Embodiment 1, the violet
light L1 emitted from the light emitting diode 220 enters the side
surface of the light guide plate 210, and is emitted as the violet
lights L1-1 and L1-2 from the upper surface 211 and the lower
surface 212 of the light guide plate 210, respectively. With regard
to the violet light L1-1, green color component light is added
thereto when the violet light L1-1 passes through the fluorescent
film 230, and the violet light L1-1 becomes the white light L2
which illuminates the main color liquid crystal display panel 110
from the side of its back surface. The color liquid crystal display
panel 110 can display optimum colors by being illuminated by white
light as the backlight.
Meanwhile, the violet light L1-2 passes through the transflective
plate 250 and illuminates the auxiliary monochrome liquid crystal
display panel 111 from the side of its back surface. Here, the
auxiliary liquid crystal display panel 111 performs monochrome
display, but because the auxiliary liquid crystal display panel 111
is illuminated in violet by the violet light L1-2, the whole
display surface of the auxiliary liquid crystal display panel 111
is in violet, the design is improved, and the appearance is
enhanced. Specifically, even if the used liquid crystal display
panel 111 is of the monochrome type which is inexpensive and low in
power consumption, the auxiliary side can also perform color
(chromatically colored) display. However, there is offered only a
single color. Therefore, even if the liquid crystal display device
is of the monochrome type, it can be designed such that, for
example, the color of the outside of the display device 100 of the
cellular phone is the same as the color which the auxiliary liquid
crystal display device performs. In this way, in the double-sided
display device according to the present invention, because the
color liquid crystal display panel can be illuminated by white
light as the backlight which is emitted from one surface of the
double-sided illuminating device, the color liquid crystal display
panel can perform optimum color display. Further, because the
monochrome liquid crystal display panel can be illuminated by
chromatically colored light as the backlight which is emitted from
the other surface of the double-sided illuminating device, the
monochrome liquid crystal display panel can perform chromatically
colored display.
Embodiment 2
By further disposing a blue light cutting film between the
transflective plate 250 and the auxiliary liquid crystal display
panel 111 in Embodiment 1 illustrated in FIG. 1, the auxiliary
liquid crystal display panel 111 can be illuminated by red light as
the backlight, and thus, the auxiliary liquid crystal display panel
can perform red display. Further, by disposing a red light cutting
film between the transflective plate 250 and the auxiliary liquid
crystal display panel 111, the auxiliary liquid crystal display
panel 111 can be illuminated by blue light as the backlight, and
thus, the auxiliary liquid crystal display panel 111 can perform
blue display.
Still further, by disposing between the transflective plate 250 and
the auxiliary liquid crystal display panel 111 a film having a
layer where a fluorescent substance is dispersed or a film having a
layer where a pigment is dispersed, the auxiliary liquid crystal
display panel 111 can be illuminated by light in an arbitrary color
(chromatically colored light) as the backlight, and the auxiliary
liquid crystal display panel 111 can perform display in the
arbitrary color.
Embodiment 3
In Embodiment 1, the LED element 222 emits blue light, the red
fluorescent substance 223 added to the sealing resin 224 emits red
light, and the fluorescent film (whitening film) 230 emits green
light, so the light L2 which illuminates the main liquid crystal
display 110 is made to be white light. However, the method to make
light illuminating the light liquid crystal display panel to be
white light is not limited to the above-mentioned example, and
various combinations can offer white light. Here, various exemplary
combinations for obtaining white light are described with reference
to FIGS. 6 and 7, in which like parts as those illustrated in FIG.
1 are denoted by the same reference numerals and a detailed
description thereof is omitted.
(1) In a first example illustrated in FIG. 6, a light emitting
element which emits blue light is used. No fluorescent substance is
added to the sealing resin. A fluorescent substance for emitting
yellow light is dispersed and mixed in the whitening film. This
makes it possible to illuminate the main liquid crystal display
panel by white light. In this case, the auxiliary liquid crystal
display panel is illuminated by blue light. In accordance with this
example, by providing a colored filter 260 having an arbitrary
color (a filter having a layer in which a pigment or a fluorescent
substance is dispersed) or a specific color light cutting filter
upstream of the auxiliary liquid crystal display panel, the
auxiliary liquid crystal display panel can be illuminated by light
of a color added by the colored filter or by light with a specific
color component thereof being cut by the particular color light
cutting filter.
(2) In a second example illustrated in FIG. 7, a light emitting
element white emits blue light is used. No fluorescent substance is
added to the sealing resin. A fluorescent substance for emitting
red light and a fluorescent substance for emitting green light are
dispersed and mixed in the whitening film. This makes it possible
to illuminate the main liquid crystal display panel by white light.
In this case, the auxiliary liquid crystal display panel is
illuminated by blue light. In this example, by providing a color
filter 270 having an arbitrary color or a specific color light
cutting filter upstream of the auxiliary liquid crystal display
panel, the auxiliary liquid crystal display panel can be
illuminated by light having a color added by the colored filter or
by light with a specific color component thereof being cut by the
specific color light cutting filter.
(3) In a third example illustrated in FIG. 7, a light emitting
element which emits blue light is used. A fluorescent substance for
emitting green light is added to the sealing resin. A fluorescent
substance for emitting red light is dispersed and mixed in the
whitening film. This makes it possible to illuminate the main
liquid crystal display panel by white light. In this case, the
auxiliary liquid crystal display panel can be illuminated by
blue-green light. In this example, by providing a specific color
light cutting filter 270 upstream of the auxiliary liquid crystal
display panel, the auxiliary liquid crystal display panel can be
illuminated by light with a specific color component thereof being
cut by the particular color light cutting filter. For example, by
using a film which cuts blue light, the auxiliary liquid crystal
display panel can be illuminated by green light, and, by using a
film which cuts green light, the auxiliary liquid crystal display
panel can be illuminated by blue light.
The above-mentioned items (1) to (3) are only examples, and the
combination may take various kinds. Further, the light emitting
element is not limited to a light emitting element which emits blue
light, and a light emitting element which emits near-ultraviolet
light can also be used. An important point is that light emitted
from the light emitting element is light including a wavelength
which can excite the fluorescent substance.
FIG. 4 illustrates exemplary combinations of a light emitting
element (LED element) and a fluorescent substance added to a
sealing material. By employing such combinations, various colors of
light can be emitted from the light source as a whole.
The double-sided illuminating device and the double-sided display
device according to the present invention can be used in, for
example, a folder type cellular phone. Specifically, the
double-sided illuminating device and the double-sided display
device can be used in a display device of various kinds of
electronic device such as a personal digital assistant in which a
main color liquid crystal display panel and an auxiliary monochrome
liquid crystal display panel are disposed back to back.
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